After an unusually long, blissful spring, summer has arrived here in Texas. School is out, and my schedule is open, free from the burden of classes. 

Despite the freedom, my time has been getting filled. Working on a mosasaur paper, prospecting new sites, social commitments and a fun day job are forming good memories, and more are coming (I'll get to that).

 

First though, my excursions from a week ago

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For the past few months, my finds have been few. Split between the duties of the semester, I haven't been getting out much, and when I have been going out, I've been looking hard for new sites, rather than returning to old honey holes. Despite my intrepid searches, no dazzling new sites have turned up, but that's the game and this kind of work is what it takes to play it. 

 

So, starving to get my hands on some fossiliferous rock, I returned to a tried a true spot that sometimes yields cool finds. It's a beautiful, tiny stream that's surprisingly accessible if one is willing to get wet and bushwhack. In its course, it reveals the blue-gray upper eagle ford formation, a Turonian layer famous for oil and exceptional marine vertebrate fossils. Above it lies the Austin chalk formation, with it's lower-most member (the Atco member) coming in at a Coniacian age and contacting the Eagle Ford. Both these layers are rich in fossils but contain different faunal assemblages, making a cool, visible case study for how marine ecosystems evolve. Some species of Ptychodus like P. anonymous can be found in the Eagle Ford, but move a few inches up into the austin chalk and they vanish. Other species like P. whipplei and P. mortoni abruptly appear in Coniacian Austin chalk layer, but do not occur in the slightly older Eagle Ford layer. The same seems to happen with Mosasaurs like Russellosaurus, so far only ever found in the Eagle Ford - an early precursor to the diverse, strongly marine adapted plioplatecarpine mosasaurs that would succeed it. 

 

 

 

 

 

My first find as I moved up the trickling waters was a partial ammonite. I was not yet in fossiliferous territory, but this wayward cretaceous traveler told me moving upstream was the right call.

 

 

 

After a short endurance run, I made it to a bend in the stream where it constricts to no more than a foot or so across. Squatting in the deep gully, with walled banks just a few feet away on either side, I noticed a brown, shelly conglomerate protruding form the gravel. This was an escapee from one of the few highly fossiliferous lenses in the upper eagle ford, and I knew to spend some time with it. 

Picking it apart, I was not disappointed. First to show was perhaps one of the most prolific sharks in the Turonian seas, Squalicorax falcatus.

 

 

Invigorated and impressed by the beautiful coloration, I kept on, eyeing every piece of the conglomerate as I knocked away. Close by came another beacon of the texas Turonian: the small, charismatic Ptychodus anonymous. Every Ptychodus tooth I find probably adds weeks to my life. 

 

Halfway through the dinner plate sized conglomerate, I could have moved on and been happy. However, still to come were the true gems of the Turonain Ptychodus species and I'm glad I stayed. 

If you look in the right places, an astute observer may notice a tiny lens, representing just a blip in geologic time, where the typical Ptychodus anonymous teeth of the formation take an odd turn in their morphology, hosting wrinkles that somewhat converge at the apex, almost like what's seen in the later Ptychodus mortoni. This unusual morphology is an undescribed species, and the work being done on it has been threatening to release for ages. At least it means that this species is getting attention  . 

 

So, trucking on, I was met with a beautiful sight:

 

 

Here it was: Species X, in crisp detail. The soft matrix made the grand reveal an easy task.

 

 

With three flawless teeth from a single rock, I was ready to move on and find the origin of this tumbler. First though, the final portion demanded attention. My jaw fell down after I dropped the next hammer blow:

 

 

For species X, this is a large tooth, and I recognized it immediately as one of the best Ptychodus teeth I've ever found. My pick and a few carefully directed hammer blows made quick work of the surrounding matrix. This is one of those weirdo teeth that flirts with the boundary of species X and P. anonymous. I think it could fall either way.

Stunning.

 

As I moved on, I enjoyed the scenery and the extant fauna. It's easy to look by the extant creatures we share our creeks with, but it's good to remember that fossils are cool because they were alive once. We can all do well to tip our hat to our creek side neighbors. 

 

Spiny softshell turtle

 

 

 

Diamondback water snake (Nerodia rhombifer)

 

 

As I left the creek, I found a reminder of my previous point, with a creature who once straddled the position of extant and extinct that never made a comeback to its original glory. Laying like a pearly beacon in the gravel was a large Bison tooth, locally extinct for at least 150 years. 

 

 

And so concluded a fossiliferous trip. With my collection tub heavy, I was now prepared to return to a challenging goal I've failed at twice before. 

 

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Though a hunter from the start (and in my heart, I suspect I always will be), my goals have been shifting academically since I first noticed my interest in fossils 3 or so years ago. In particular, I've been assisting in mosasaur research, on the specimen my brother and I found. I hope this will be the first of many that I will work on. But I digress...

 

One of the richest fossil assemblages of mosasaurs in the world is in the Maastrichtian of morocco. There are a few reasons:

1) Coastal Africa was a source of up-welling, shallow waters, and abundant food.

2) The chemical environment of the moroccan phosphates was conducive to preserving fossils

3) Mosasaurs were very diverse during the Maastrichtian, arriving on fantastical dentitions, unique body plans,  and varied (even segregated) feeding strategies to survive. This is thought to be niche partitioning, where species adapt very specific methods of life to avoid competition with other species like them. 

 

The third point implies that mosasaurs everywhere should be diverse during the Maastrichtian. Due to their sheer success at the end of the cretaceous, niche partitioning must have been inevitable, driving high rates of speciation. I don't think that Maastrichtian morocco was all that unique during that time. There is a selection bias towards fossils being discovered there due to the commercial digging and mining activity, but as far as paleo environments, other shallow seas likely rivaled morocco in diversity. 

 

The most famous shallow cretaceous sea, at least in my corner of the world, is the western interior seaway, bisecting the north american continent. During the Maastrichtian, it was a shadow of its former self, but nonetheless a substantial body that drowned much of Texas. Yet, despite that, Texas has a very poor record of Maastrichtian mosasaurs. 

 

One reason, perhaps, is the tsunami that the cretacoeus ending Chicxulub meteor generated. Much of the upper Maastrichtian marine strata in texas is a tumbled mess due to the apocalyptic force of the wave that crushed Texas that spring day 66 million years ago. The tsunami ripped up millions of years of strata in some places, now visible as tsunamite deposits with Maastrichtian debris branching up into the Danian deposits. 

 

However, some spots survived, with the K-Pg line visible in some places in Texas. Elsewhere, early maastrichtian strata stayed in tact, spared by its depth in the strata at the time. 

 

My goal was to find maastrichtian marine strata and prospect for mosasaur material. Because of how poor the maastrichtian record is here, coupled with the high degree of endemism in maastrichtian mosasaurs, I suspect that the Texas maastrichtian hides many undescribed species.

 

The problem is that Texas maastrichtian outcrops are uncommon, and if you're lucky enough to find one, they chew you up and spit you out. Worse, they're poorly sorted on geologic maps, which often just display groups instead of formations. Some formations are better than others, so using a map means you have to do the leg work and filter out the formations you weren't looking for in person, one by one. After several challenging excursions in barren rock with nothing to show but a sack of woe, I'm not surprised Texas has such a poor record of maastrichtian vertebrates. 

But, this is the game  

 

Two excursions this year into my best maastrichtian spot have left me with large oysters (Exogyra costata) but nothing else. However, invigorated by yesterday's Turonian success, I set out with maastrichtian mosasaurs on my mind.

 

Site 1: A partial success. After long last and two other failed attempts, I finally found an outcrop of the upper taylor marl (which lies on top of the Pecan gap formation, which itself lies over the lower taylor marl (AKA the Ozan formation)). Though not maastrichtian, this middle campanian formation is a tad younger than the well explored Ozan, and could promise different animals. I found it lithologically indistinguishable from the Ozan formation, but I'm sure a geologist could separate them on sight. Though some research promises that in it's upper reaches, bountiful, spectacular ammonites could be seen, I saw nothing. In fact, the only difference I could make of it from the Ozan is that it has fewer fossils. I must come back!  

 

Site 2, that same afternoon:

My old nemesis, a beautiful maastrichtian cliff of unknown geologic affinities. My suspicion lies with a Kemp clay ID, but I'm not too sure. Two times this enormous, searing outcrop has turned me away, burned and empty handed. Due to the sheer extent of this outcrop, I suspect my best chance for maastrichtian mosasaur material lies here, despite the unforgiving rocks. 

 

As I began, I crossed the creek below to the flat opposing bank, in case it gave me views of more outcrops down stream. A small gar, perhaps 3 feet or so, meandered through the murky water in front of me as I crossed, while peaceful oak/elm savanna rose from the banks before me. 

 

I trod though bushels of grass and vines, no different than usual, when an explosive, fiery pain scorched my calf. Chewing my tongue and resisting the urge to immediately claw my leg, I made haste back to the water to submerge myself.

I have the benefit of what seems to be a partial immunity to poison ivy. I tread through jungles of it, even seeking out outcrops choked in it as my advantage because it deters other hunters. Outbreaks are rare and small for me, often only coming days after my excursions. Whatever plant did this to me was of evil crop, and I have no idea the culprit. The cool water did little, and despite my leg being wet and sunscreen smeared, the oil/spines took strong effect. It took great power of will not to touch the agitation for the next 10 minutes, but then, suddenly as it came, the sensation disappeared and my leg was fine again, though a bit sensitive. Very unusual experience. 

 

For my sufferings though, I did not come away empty handed. Early on, as I worked a tumbled boulder, I paused a hammer blow to see this where it would've landed:

 

 

Heart attack averted, I plucked it from it's resting position, and in my hand found the broken apex of a mosasaur tooth - my first from maastrichtian strata. Though diminutive enough to consider fish, the ornamented enamel, notable thinness of the enamel, and bicarinate nature point me to mosasaur. 

 

What's more, the ridges seem unusually strong for a tooth apex. Not something I expected, and so this supports my idea that there is a hidden diversity of unseen mosasaurs from Texas maastrichtian waters.

 

 

 

 

 

Not the complete, articulated skeleton every hunter fantasizes about, but a tantalizing clue that I'm in the right place. Though sometimes punishing, I can't wait to return to this place